There is probably a huge amount of good stuff available from the people who are working actively with XmlRpc, Biztalk and other approaches to web services. More too from XML writers such as [http://uche.ogbuji.net/uche.ogbuji.net/ Uche Ogbuji], who has put much good stuff on IBM's developerworks site, among other things.
[http://wwwsearch.sourceforge.net/bits/clientx.html Python web-client programming general FAQs]
[http://docs.python.org/lib/module-urllib.html urllib -- Open arbitrary resources by URL]
[http://docs.python.org/lib/module-urllib2.html urllib2 -- extensible library for opening URLs]